This application is based upon and claims priority of Korean Application Nos. 99-14286 and 99-24296, Apr. 21, 1999 and Jun. 25, 1999 respectively, in the Korea Patent Office, the disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical recording medium, and more particularly, to an optical recording medium, and a recording/reproduction method therefor, in which a header, used for addressing, is disposed between adjacent land and/or groove tracks, a basic addressing unit having a first predetermined size is assigned, and a minimum recording unit having a second predetermined size is assigned.
2. Description of the Related Art
A mass recording capacity and high speed reproduction of optical discs is required for recording and/or reproducing high definition (HD) images. Accordingly, a multimedia technology of recording and/or reproducing a large quantity of information on and/or from a recording medium such as a rewritable or read only HD-digital versatile disc (DVD) is required.
Various methods have been suggested for satisfying the requirements of mass recording capacity and high speed reproduction. For example, the area of a disc or the rate of rotation may be increased. However, such methods are not practical since they require an increase in the sizes of a disc and a player and also result in increased production cost. Thus, it is preferable to increase the recording density per unit area of the disc, rather than increase the area of a disc at the rate of rotation.
The size of a recording laser spot is proportional to the laser wavelength and inversely proportional to the numerical aperture (NA) of an object lens. Accordingly, to increase the recording density per unit area of the disc, the laser wavelength should be decreased, or an object lens having a high numerical aperture should be used to decrease track pitch.
In such an optical disc, particularly, a recordable disc, a recording area for recording data in regular units is segmented into regular basic recording units (e.g., sectors or frames). In writing or reading data to or from an area which is a physically segmented basic recording unit, it is essential for an optical pick-up unit (hereinafter, referred to as a pickup) to move to the exact position of the corresponding area at high speed without error.
To allow a pickup to move to an exact position a header field in the optical disc is utilized. In a 2.6 gigabyte (GB) or 4.7 GB DVD-RAM, a header field for each sector is assigned 128 bytes. The information of the header field is written on the disc in the form of pre-pits during the manufacture of a substrate. The header field is composed of a variable frequency oscillator region for a phase locked loop (PLL), a physical identifier (PID) region to which a sector number is assigned, an ID error detection (IED) region for storing ID error detection information, and a postamble (PA) region for regulating modulation. A header field is appropriately disposed at the front portion of a sector. When a pickup accesses a desired position, a microcomputer (not shown), recognizing signals which are stored in the header field and picked up by the pickup, can detect the sector number and sector type of a sector corresponding to the accessed position and determine whether the sector is included in a land track or a groove track. Moreover, the microcomputer can perform servo control using the picked up signals.
Representative examples of the structures of conventional headers are shown in FIGS. 1A through 1D. xe2x80x9cGxe2x80x9d indicates a groove track, and xe2x80x9cLxe2x80x9d indicates a land track. In FIG. 1A, a header is located between adjacent land and groove tracks. In this structure, the track pitch is narrowed as the recording density increases, thus, crosstalk between adjacent tracks may occur.
In FIG. 1B, a single header is located at the boundary between a land track and a groove track. The single header can be used for a pair of land and groove tracks. This structure produces more advantageous signals than the structure of FIG. 1A since the width of a header of FIG. 1B is wider than the width of the header in the structure of FIG. 1A. However, since the arrangement of headers is unbalanced, this structure is susceptible to a tracking offset (or margin).
In FIG. 1C, a header is located between adjacent groove and land tracks such that headers are not adjacent between the adjacent land and groove tracks. In this structure, crosstalk does not occur. However, servo control compensation cannot be achieved. Therefore, an additional servo control compensation method is required.
The structure of FIG. 1D is used in a DVD-RAM. Compared to the structure of FIG. 1C, a header is shifted by half of a track pitch. The structure of FIG. 1D compensates for the drawbacks of the structures of FIGS. 1A, 1B and 1C. However, since half of a header is offset from the other half of the header by one track pitch, the manufacture of this structure is more difficult compared to the other structures. For this reason, particularly in a 4.7 GB DVD-RAM having the structure of FIG. 1D, the signal characteristics (jitter) of first and second header fields may not be the same as those of third and fourth header fields. The content of the header field will later be described with reference to FIGS. 4A and 4B.
To provide mass storage capacity of HD image data, for example, 15-20 GB, a recordable area (user data area) needs to be increased by minimizing not only track pitch but also areas (overhead) other than a recording area. The size of header fields in a DVD-RAM is about 5% of the physical sectors of the DVD-RAM. To achieve high density recording, by decreasing the size of an overhead, a structure for decreasing header fields, that is, a structure in which a header field is located at the boundary between adjacent tracks as shown in FIGS. 1B and 1D, is necessary. However, as described above, in the structure of FIG. 1B, servo control compensation, including track offset, must be implemented.
FIGS. 2A through 2C show examples of a typical track structure. FIG. 2A shows a concentric circle track structure. FIG. 2B shows a double spiral track structure. FIG. 2C shows a single spiral track structure used in a DVD-RAM. Reference numeral 1 indicates a groove track, reference numeral 2 indicates a land track, and reference numeral 3 indicates a header assigned to each basic recording unit (here, a sector).
Particularly in the single spiral track structure of FIG. 2C, a land track can be distinguished from a groove track at a land/groove track transition position 4, at which the land track transitions to the grove track or the groove track transitions to the land track, based on a detection of the land/groove track transition position signal and according to the arrangement of a header therein.
For discs having the single spiral track structure of FIG. 2C and the header structures of FIGS. 1B, 1C and 1D, the header structures of the discs, at a position at which groove tracks are connected to land tracks, are shown in FIGS. 3A, 3B, and 3C. It can be determined whether a sector including a header belongs to a land track or a groove track using a header signal (for example, a two-divisional signal of a photodetector) at a position at which the groove track is connected to the land track.
Accordingly, in the header structure of FIG. 1A, it can be determined whether a sector including a header belongs to a land track or a groove track, at a position at which the land track is connected to the groove track, from pre-pit information within the header. In the header structure of FIG. 1B, it can be determined whether a sector including a header belongs to a land track or a groove track, at a position at which the land track is connected to the groove track as shown in FIG. 3A, from pre-pit information within the header or from a header signal. In the header structure of FIG. 1C, it can be determined whether a sector including a header belongs to a land track or a groove track at a position, at which the land track is connected to the groove track as shown in FIG. 3B, from pre-pit information within the header or from a time difference between header detections. In the header structure of FIG. 1D, since a header extends over a land track and a groove track and half of the header is offset from the other half of the header by one track pitch, it can be determined whether a sector including a header belongs to the land track or the groove track, at a position at which the land track is connected to the groove track, as shown in FIG. 3C, from pre-pit information within the header or from a header signal.
In FIG. 1B, the header can be commonly used for indicating the land and groove tracks since it extends over the land and groove tracks. However, when information for indicating whether the sector, including the header, belongs to the land track or the groove track is recorded in a header of the same length as headers in other header structures (FIGS. 1C and 1D), it is not advantageous to utilize the structure of FIG. 1B because the other structures include offsetting half of the header from the other half of the header by one track pitch.
FIGS. 4A and 4B show an example of the content of a conventional header. In the header of FIG. 4A, employed in a method of performing servo control at a constant angular velocity (CAV), the address of a sector is represented by a track number and a sector number. Alternatively, in the header of FIG. 4B, employed in a method of performing servo control at a zoned constant linear velocity (ZCLV) for use in a DVD-RAM, since the number of sectors in each track is different, addressing information is represented by only a sector number without using a track number. The sector number is embedded in a PID region of FIG. 4B.
In a case in which a third header field and a fourth header field are offset from a first header field and a second header field by one track pitch (FIG. 1D), the first and third header fields have a 36-byte VFO1 which is longer than an 8-byte VFO2 included in the second and fourth header fields as shown in FIG. 4B. When the header is arranged without offset, the length of VFO1 in the first and third header fields may be set to 8 bytes which is the same as assigned to VFO2 in the second and fourth header fields. Further, the number of header fields can be decreased because the header fields have the same signal characteristics.
FIG. 5 shows a slice level and a PID signal provided through a first channel indicating a header detection signal corresponding to a change in a header, that is, a sum signal of two-divisional signals of a photodetector, when the header is arranged with offset. Referring to FIG. 5, fluctuation occurs at a position A at which the first and second header fields are connected to the third and fourth header fields and at the slice level, which is used for slicing, for a predetermined period of time. Accordingly, the magnitude of VFO1 (represented by reference numeral 3) of the third header field is set to 36 bytes which is the same as that of VFO1 (represented by reference numeral 1) of the first header field. A drive detects only the latter 8 bytes from each VFO1 in the first and third header fields, not the first 28 bytes.
When a HD disc of 20 GB or more, which will be developed in the near future, uses a complementary allocated pit address (CAPA) structure (FIG. 1D), used in a conventional 4.7 GB DVD-RAM or a structure in which headers are shifted by half of the track pitch (Tp/2), for common use by land and groove tracks as shown in FIG. 1B, base jitter problems do not occur. However, the margin characteristics become much worse compared to a conventional 4.7 GB disc or a HD disc having an on-track structure, that is, a structure in which headers are not shifted (off-track=0), as shown in FIG. 6.
To solve the above problems, a first object of the present invention is to provide an optical recording medium having a sector structure in which a user area of a basic recording unit is physically divided into units of a first predetermined size (4 KB) and in which the user area is logically divided into a second predetermined size (2 KB) in order to reduce the amount of overhead.
A second object of the present invention is to provide an optical recording medium for improving the reliability of a system by disposing headers in the middle of land and groove tracks in the form of physical pits.
A third object of the present invention is to provide a method of recording and reproducing user data in and from an optical recording medium having headers between adjacent land and/or groove tracks, and having sectors which are basic recording units physically divided into units of a first predetermined size (4 KB) and where a user area within the basic recording units is logically divided into minimum recording units of a second predetermined size (2 KB).
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above objects and other objects, the present invention provides an optical recording medium including a header area, which indicates address information and is added to basic recording units of a first predetermined size, wherein a user area within the basic recording unit is divided into minimum recording units of a second predetermined size.
To achieve the above objects and other objects, the present invention provides a method of recording/reproducing information on/from an optical recording medium in an optical recording medium recording and reproducing apparatus. The method includes the steps of recording address information in a header area added to each basic recording unit of a first predetermined size, and dividing a user area within the basic recording unit into minimum recording units of a second predetermined size and recording information in the minimum recording units.
The method of the present invention also includes the steps of reading the address information in the header area from the optical recording medium and addressing the basic recording unit, and reproducing data in the user area in the minimum recording units within the addressed basic recording unit.